1. Field of the Invention
The present invention relates generally to a distribution cable deployed in a fiber optic communications network, and more specifically, to a fiber optic distribution cable having a flexible overmolded mid-span access location and a tether for providing access to at least one preterminated optical fiber of the distribution cable.
2. Description of the Related Art
Optical fiber is increasingly being used for a variety of broadband communications including voice, video and data transmissions. As a result of the increasing demand for broadband communications, fiber optic networks typically include a large number of mid-span access locations at which one or more optical fibers are terminated from a distribution cable. These mid-span access locations provide a distribution point from the distribution cable leading to another distribution point, or a drop point from the distribution cable leading to an end user, commonly referred to as a subscriber, thereby extending an “all optical” communications network closer to the subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-curb”(FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH), or “fiber-to-the-premises” (FTTP), referred to generically as “FTTx.” Based on the large number of mid-span access locations and the unique demands of optical fibers and optical connections, a distribution cable is needed for routing and protecting optical fibers, and for providing access to terminated optical fibers at numerous mid-span access locations in an FTTx network. A distribution cable is also needed for permitting optical fibers that are accessed and terminated from the distribution cable at mid-span access locations along the length of the distribution cable to be optically connected with optical fibers of one or more fiber optic branch cables or fiber optic drop cables.
In one example of a fiber optic communications network, one or more drop cables are interconnected with a distribution cable at a mid-span access location. Substantial expertise and experience are required to configure the optical connections in the field. In particular, it is often difficult to identify a particular optical fiber of the distribution cable to be optically connected with an optical fiber of a drop cable. Once identified, the optical fiber of the distribution cable is typically joined directly to the optical fiber of the drop cable at the mid-span access location using conventional splicing techniques, such as fusion splicing. In other instances, the optical fiber of the distribution cable and the optical fiber of the drop cable are first spliced to a short length of optical fiber having an optical connector mounted on the other end, which is generally referred to in the art as a “pigtail.” The pigtails are then routed to opposite sides of a connector adapter sleeve to interconnect the drop cable with the distribution cable. In either case, the process of configuring the mid-span access location is not only time consuming, but frequently must be accomplished by a highly skilled field technician at significant cost and under field working conditions that are less than ideal. In situations in which a mid-span access location is enclosed within a conventional splice closure, reconfiguring optical connections within the splice closure is especially difficult, based in part on the relatively inaccessible location of the closure, the limited workspace available within the closure, and the inability to readily remove the closure from the distribution cable. Further, once the spliced optical connections are made, it is labor intensive, and therefore relatively costly, to reconfigure the optical connections or to add additional optical connections.
In order to reduce installation costs by permitting less experienced and less skilled technicians to make optical connections and to reconfigure optical connections at mid-span access locations in the field, communications service providers are increasingly pre-engineering new fiber optic networks and demanding factory-prepared interconnection solutions, commonly referred to as “plug-and-play” type systems. There are currently several methods to build a distribution cable assembly for successful deployment and field installation. In one example, the distances between network distribution or termination points are measured with great accuracy and a factory-prepared distribution cable assembly is built with mid-span access locations positioned precisely at the distribution or termination points. However, in this instance the length of the distribution cable between mid-span access locations must be exact, and the deployment of the distribution cable must be performed accurately so that no extra cable length is used between or at the distribution or termination points. If extra length of distribution cable is used, the incorrect placement of even one mid-span access location will have a compounding effect on the position of each downstream mid-span access location. As a result, all downstream mid-span access locations will be out of position and the length of distribution cable will come up short at the end of the cable run. Obviously, measuring the absolute distances between mid-span access locations and building a distribution cable assembly with accurate distances between mid-span access locations is a difficult undertaking. Furthermore, any error in the manufacturing process may result in the entire distribution cable assembly be unusable, and therefore scrapped. In another example of a distribution cable assembly, an excess length of cable (i.e., slack) is intentionally built into the distribution cable at each mid-span access location to insure that the distribution or termination point can always be positioned in the field at exactly the correct location. The obvious drawbacks with such a distribution cable assembly are the cost associated with the excess lengths of cable and the associated need to store the cable slack in an aesthetic and practical manner.
In addition to the problem of manufacturing a distribution cable assembly having the network distribution or termination points in the proper locations, there are also problems encountered with using conventional components to optically connect the optical fibers of the distribution cable with optical fibers of branch cables or drop cables at the mid-span access locations. For example, rigid enclosures are typically used to protect the section of the distribution cable that must be exposed to access the appropriate optical fibers and the splices. Distribution cables provided with conventional enclosures tend to be large in size and inflexible, and thus, unable to satisfy common deployment constraints, such as being wound onto a reel, deployed through conduits having a relatively small inner diameter or significant bends, or deployed through conventional aerial lashing equipment, such as sheaves and rollers. Furthermore, such enclosures are often structurally complex and difficult to install.
Accordingly, there is a specific and unresolved need for a factory-prepared fiber optic distribution cable including at least one mid-span access location for providing access to one or more preterminated optical fibers that has a small enough diameter and is flexible enough to be wound onto a reel, deployed through a conduit having a relatively small inner diameter or significant bends, or deployed using conventional aerial lashing equipment. In addition, there is a specific and unresolved need for a factory-prepared fiber optic distribution cable that does not require a highly skilled field technician or extensive field labor to interconnect optical fibers of the distribution cable with optical fibers of a branch cable or drop cable and to reconfigure the optical connections after the initial installation of the distribution cable. To satisfy these needs, what is needed is a factory-prepared fiber optic distribution cable assembly including at least one relatively small diameter, flexible mid-span access location and a tether attached to the distribution cable at the mid-span access location that provides a short length of cable slack to permit the distribution or termination point to be accurately positioned at the correct location in the fiber optic communications network.